1. Field of the Invention
The present invention relates to a power storage device and a method for manufacturing the power storage device. Note that, in this specification, power storage devices refer to part or all of devices each having a function of storing electric power.
2. Description of the Related Art
In recent years, power storage devices such as lithium-ion secondary batteries and lithium-ion capacitors have been developed.
An electrode for the power storage device is manufactured by providing an active material over a surface of a current collector. As an active material which occludes lithium, a material which can occlude and release ions serving as carriers, such as graphite or silicon, is used. In particular, silicon has attracted attention because it has a higher theoretical capacity than graphite and is advantageous in increasing the capacity of power storage device.
For example, Non-Patent Document 1 discloses a lithium-ion secondary battery formed using whisker-like single crystal silicon (silicon nanowires) as an active material. Non-Patent Document 1 suggests that in the case where whisker-like silicon is used, the structure of an electrode is not easily damaged even when the volume of silicon is changed due to occlusion and release of lithium ions, resulting in increases in charge/discharge characteristics.